<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div {
            width: 300px;
            height: 300px;
            background-color: pink;
        }
        .one {
            /* margin的复合属性和padding一样 */
            margin-bottom: 20px;
        }
    </style>
</head>
<body>
    <div class="one">1</div>
    <div>2</div>
</body>
</html>